石墨烯力常数和弹性波波速随温度变化规律研究

发布时间：2018-12-13 04:46

【摘要】：在哈里森键联轨道法框架下,考虑到原子的短程相互作用和原子的非简谐振动,建立石墨烯弹性模型并求出原子振动的简谐系数和非简谐系数.在此基础上,确定了石墨烯的力常数随温度和形变势参量的变化关系式,以及弹性波波速随温度和形变势参量的变化关系式,并探讨了原子非简谐振动对它们的影响.结果表明:(1)石墨烯的力常数和弹性波波速均随温度升高而非线性减小,但有不同的变化特征:在C_(11)、C_(12)、C_(44)这三个力常数中,以C_(12)随温度的变化最大,以C_(44)的变化最小;纵波波速随温度的变化要大于横波;(2)石墨烯的三个力常数随形变势参量的变化有不同的特征:C_(11)随η和γ的增大而增大、而C_(12)则随η的增大而减小,随γ的增大而增大;C_(44)随η的增大而增大,而几乎不随γ而变;(3)若不考虑原子振动的非简谐项,则石墨烯的力常数和弹性波波速均为常数.考虑到非简谐项后,不仅它们均随温度的升高而减小,而且,非简谐情况的力常数C_(ij)和弹性波波速v_i与简谐近似的值C_(ij)~0、v_i~0的差|C_(ij)-C_(ij)~0|、|v_i-v_i~0|均随温度的升高而增大,即温度愈高,非简谐效应愈显著.
[Abstract]:In the framework of Harrison bond orbital method, considering the short range interaction of atoms and the anharmonic vibration of atoms, an elastic model of graphene is established and the harmonic and anharmonic coefficients of atomic vibration are obtained. On this basis, the relations of the force constants of graphene with temperature and deformation potential parameters, and the relationship between elastic wave velocity and temperature and deformation potential parameters are determined, and the influence of atomic anharmonic vibration on them is discussed. The results show that: (1) the force constants and elastic wave velocities of graphene decrease nonlinearly with the increase of temperature, but have different characteristics: among the three force constants, C _ (11), C _ (12), C _ (44), The change of C _ (12) with temperature is the biggest, and that of C _ (44) is the least. The variation of P-wave velocity with temperature is larger than that of S-wave. (2) the three force constants of graphene have different characteristics with the change of deformation potential parameters: C11 increases with 畏 and 纬, C12 decreases with increasing 畏 and increases with 纬; C _ (44) increases with the increase of 畏, but almost does not change with 纬. (3) if the anharmonic term of atomic vibration is not considered, the force constant and elastic wave velocity of graphene are constant. Taking into account the anharmonic term, not only do they decrease with the increase of temperature, but also the force constant C _ (ij) and elastic wave velocity v _ T _ I of the anharmonic case and the value C _ (ij) ~ 0 of the simple harmonic approximation are taken into account. The difference of v_i~0 C _ (ij)-C _ (ij) ~ 0 and v_i-v_i~0 increased with the increase of temperature, that is, the higher the temperature, the more significant the anharmonic effect.
【作者单位】：重庆文理学院电子电气工程学院;
【基金】：重庆市基础与前沿研究项目(cstc2015jcyj A40054) 重庆文理学院校级重点项目(Z2015DQ11) 重庆市教委科学技术研究项目(KJ1501105) 永川区科委自科基金(Ycstc,2015nc2001)
【分类号】：O613.71

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